It is well accepted within the tire manufacturing industry that

It is well accepted within the tire manufacturing industry that use of a "belt edge layer" or as referred above as an extra layer, virtually eliminates belt edge separation. As a rubber tire moves on the road, it generates tremendous heat. As steel belts heat up, they expand and want to pull away or separate from rubber. The use of nylon belt edges has been in use since radial tires were first developed in the 1970s. Firestone could achieve cost savings from eliminating this extra layer.